The invention relates to a lens having a curved surface and a plane surface on opposite sides, and a holding edge molded on the lens edge as well as a supporting edge projecting from the plane surface and molded on the holding edge, to use of the lens and to a method of manufacture of the lens.
J59-177506A describes lenses of a projection objective wherein the two external lenses of the objective have a supporting edge which projects towards the plane lens surface and is designed as stepped. The shoulder thereby produced is used for support on a further lens, namely a biconvex lens, with the aim of specifying a distance between the lenses.
JP59-157603A shows two lenses which have supporting edges having projections with inclined surfaces provided on their outer circumference. As a result of this configuration, importance is placed on high precision and stability of the edges.
In this respect, the supporting edges in both of the foregoing cited prior art references are designed and constructed according to their mounting configuration with further lenses.
Such lenses have conventionally been pressed into an aspherical shape on one side and subjected to a grinding process to form a plane surface on the other side. This grinding process, which is followed by another polishing process, is carried out after passage through a cooling furnace. The passage through a cooling furnace is necessary to specifically cool the still hot blank so that stresses inside the lens can be removed. In this case, however, the blank must be placed on a conveyer belts, whereby the supporting surface of the lens is disadvantageously influenced. However, if the passage through the cooling furnace is followed by a grinding process, these surface deformations are eliminated.
However, this method has the disadvantage that additional grinding and polishing processes are required.